Sliding sleeve valves have been a part of oilfield completions for many years, traditionally shifted with a tool carried on a wireline. In the past few years, these sleeves have been run in increasingly deviated wells, including horizontal wells. In these cases, wireline has not been a suitable method of conveying the shifting tools, and tubing has had to be employed, both threaded and coiled tubing. Some specialized shifting tools have been made for these applications, most of them based on wireline tool designs. One drawback to this has been the feedback of when the shifting operation has been completed. Traditional sliding sleeves and wireline shifting tools have relied on the fact that the weight of the wire is not a significant force, compared to the force to shift a sleeve, or the weight of the tools used. Jarring forces were used to shift sleeves. The move towards tubing-conveyed shifting tools means that the force required to shift the sliding sleeve is now a small portion of the weight of the tubing string. One method employed to overcome this is to increase the force required to shift the sleeve until it is a significant force. This has the disadvantage that if well debris adds to the required force, then forces can become unacceptably high.
To overcome this, a new feedback method has been developed. This new shifting tool has two distinctly different sets of keys. When the sleeve has shifted, a significant force can be applied to it, over and above what it would normally take to shift. If the action of shifting the sleeve is repeated, the shifting tool will not reengage if the sliding sleeve has shifted fully. If it has not, then the shifting action is repeated with increasing force until shifting is completed.
A second feature of this shifting tool is that it can be released from a sliding sleeve by application of a predetermined force. Almost all shifting tools on the market have an emergency release system which is commonly a shear mechanism. When the shear force of the mechanism is reached, the tool retracts the shifting mechanism, allowing the shifting tool to pass. The tool cannot now engage this sleeve or any other until it is removed from the well and the shear system replaced. This new shifting tool can be sheared free in the same manner, but it can also be equipped with a resettable mechanism which allows the tool to be released form the sliding sleeve, but instead of requiring the tool to be removed from the well and redressed, the tool resets itself back to the normal running position. This can save considerable trip time when multiple shifting operations have to be made in a single well. To pass beyond a sliding sleeve which is stuck, a tool which shears out would not allow passage. A shifting tool that can reset itself can pass through that stuck sliding sleeve and shift subsequent sliding sleeves.
The shifting tool can also be outfitted with a hydraulic or mechanical selective mechanism which keeps all the shifting mechanisms retracted, allowing the tool to pass up and down the well, shifting only those sliding sleeves which the operator selects. The tool has the advantage that, through selection of appropriate forces, it can be conveyed and operated using any method, including wireline, coiled tubing, threaded and jointed tubing.